Magnetic speedometer.



BEST ZWMLABLE COPY Y "J. K. STEWART. MAGNETIC) SPEEDOMETER. APPLICATION .FILBD AUG. 5, 1910.

1,070,378, Patented Aug. 12,1913.

I, Z a 7 I J5 Z6 ile/PK UNITED STATES" PATENT carton.

JOHN K. STEWART, OF CHICAGO, ILLINOIS, ASSIGNOR TO STEWART-WARNER SPEEDOMETER CORPORATION, OF VIRGINIA.

MAGNETIC SPEEDOMETER.

Specification of Letters Patent.

PatentedAug. 12,1913.

Application filed August 5, 1910. Serial No. 575,735.

vide an improved construction of magnetic speedometer adapted to afi'ord compensation for the change, which results from the change of temperature, in resistance of the non-magnetic element or drag disk.

It consists in the features and elements of construction shown and described as indicatedin the claims.

In the drawings Figure 1 is a vertical axial section of a magnetic speedometer embodying this invention. Fig. 2 is a section at the line 22 on Fig. 3 showing in plan view the principal parts embodying the invention. Fig. 3 is a partly sectional elevation of the device taken at right angles to the view of Fig. 1.

The speedometer to which this invention is shown applied in the drawings is in eneral of the character and construction wiich is shown in my application Serial No. 527,179, filed Nov. 10, 1909, and the several parts which are shown in that application will be referred to and described only so far as necessary to indicate their relation to the parts constituting the present invention and their coeperationtherewith for the purposes of this invention.

This instrument comprises a case, 1, from the bottom of which a rigid post, 2, extends up within the case adording a bearing for a. rotary element which comprises a magnet, 4, in the form of a cylindrical annulus longitudinally rifted at one side, the poles being at opposite sides of the rift, the magnet being mounted rigidly upon a non-magnetic carrier, 3, which also carries anarmature, 8, whichis a cylindrical annulus of thin soft steel or iron whose interior diameter is enough greater than that of the magnet, 4, to cause a narrow annular space, 9, to be formed between the two when both .are mounted on. the carrier as shown. The lower end of the carrier is provided with a bevel gear rim, 20, with which it is engaged by a pinion, 21, on a shaft, 22, which extends land havin' up; short 1 one into the case from the outside for rotating the magnet by a connection, not shown, of the pinion shaft, 22, with the rotating part whose speed is to be measured. The post, 2,

is expanded at the base and cut through or channeled at the lower end across the axis,

making it bifurcated, and it is axially bored 1 from top to bottom,-that'is, to the'channel which divides the lower end. The non-magnetic element or drag disk, 14, is of inverted cup form, mounted on a spindle, '13, which extends down tothe axial bore, 2, of the post 2, the cylindrical portion of the cup extending into the annular space 9, between the magnet Land the armature 8. A plate 15, mounted upon shoulders 1 of the case closes at the top the chamber in which the magnet armature and drag disk are associated and afiords an upper bearing for the spindle 13, which extends through said plate, carrying at its upper end the index hand 19, and hav,-

ing connected to it just above the plate 15, the inner end of the biasing spring 16, whose outer end is fastened to the plate at the stud 15, for the well understood function of biasingthe drag disk to a predetermined posi tion of rest from which it'maybe deflected by the rotation of the magnet. The spindle 13 is stepped at its lower end in a step-bearing which is illustratedias a jewel 6,'-mount-' ed in a cup 7, and to support this step hearing in a manner which Wlll permit itsmove ment up and down to vary the depth to which the cylindrical member of the drag disk 14 intrudes into the annular space between magnet and annatuliathere is pro-- .vided a lever system which will now bedescribed andin which the present invention is embodied. 25 is a plate in the form of a yoke onfork,

which has the function of supportihgkthe lefveg system hereinafter describecip i and igre; ferred to as a, lever supportji cured rig dly ,tothe bottom of the case, ex,-

tending so as tot'erininate its foiiE-arms at too points at'diametrically; pppositelsides ofjthc Ur ne' tdei there is fulcrumed s len 26, "ex ending horizontally toward theifiqflw I e levengzp ort 25,

the-side of'the ease} Thelbfng arm otthe end of the lever support, said engagement being near the fulcrum of the last-mentioned lever, which extends alongside the lever 26 to the center of the case, where it terminates under the jewel cup 7, and ailords lodgment and support for the latter. The abutment 28, against which, the short arm of the lever 26 bears, is preferably a screw set through the wall of the case and adjustable therethrough to properly position the two levers.

The material of the lever support 25 preferably steel, and that of the case is bronze or brass, or other alloy, having a considerably greater coeificient of expansion than the material of the lever support 25. From this relative character of the materials of the case and lever support, respectively, it results that the lowering of temperature, causing the case to shrink relatively to the lever suppurt, makes the case press inwardly against the short arm 2G of the lever 26, with the result of lifting the inner end of the lever 26 a distance as many times greater than the 'diilerence of expansion of the case and lever support as the product of the ratios of the long and short arms of the respective levers. Thus, if the longer arm of the lever 26, measuring from its fulcrum to the pin 26 is forty times the length of the short arm, measuring from the fulcrum to the point of impingement of the abutment 28 onthe short arm 26, and the long arm of lever, 27, measuring from its fulcrum to the point of lodgment of the jewel cup, is five times the length of its short arm, measuring from the fulcrum oi the bearing of the pin 26 in the slot 27, a relative shrinkage of the case with respect to the lever support of one-thousandth of an inch will cause the lifting of the jewel cup two-hundred times as Inuch,-on edifth of an inch. The proportions indicated are practically obtainable ul ith in the usual size of instruments of this 0 ass.

In order to obtain the full advantage oi the difference in expansion and contraction in the case and lever support respectively, the lever support should be stopped on the case at the end opposite that at which the lever 26 is fulcrumed, so that the difference of expansion of the two parts (case and lever) for the entire diameter of the case will be the amount of the initial movement for operating the levers. In order that the lever support may be thus stopped and at the same time may obtain a better support on the case than if it were merely fastened to the case at said end opposite the fulcrum 26, the attachment otthelever support to the case is made by a single screw 25 at one side of the center post 2, where the bottom of the case is provided with a broad top boss 1, upon which the lever support rests and against which it is bound by the screw 25 invasive and the abutment screw 28 is adjusted so that the end 25 of the lever support 25 against the side of the case, when the jewel cup 7 is at the proper elevation for positioning the biasing element of the drag dish 1el-pro erly with respect to the magnet, to afford the correct indication by the speech ometer, from which it will result that in any subsequent changes of temperature, the weight of the biased element and its spindle, and the downwardmeaction of the biasing spring, tending to hold the inner end of the lever 27 downward, will cause the end 25' oi the lever support 25 to be kept against the side of the case, thus giving, as designed, the value of the difference of expansion of the lever and case for the full diameter of the case for the purpose of operating the lever couple or system, and adjusting the biased element 14 of the instrument.

The dimensions above given and illustrated, and in accordance with which the device is constructed, are merely illustrative of the mode and general range of action do sired and. obtainable in the device. The total range of movement of the spindle and nonmagnetic biased element or drag disk 14, which will result from change of tempera ture from the lowest to the highest temperature,say from O to 110 E ior varying the depth to which the biased element intrudes into the space between the magnet and the armature, is readily calculable, so as to be suflicient to compensate for the change in electrical resistance of the drag dish, due to the same change of temperature. It will be obvious that the proportions of the walls, and the relations of their respective dimensions to the diameter of the case,\ will depend upon the particular materials chosen for the case and lever support respectively,that is, upon the difference between their respective coeflicients of expansion; also, it will be obvious to one familiar with the subject that the width or height of the cylindrical member of the drag disk or element 14: must be taken into account, since the ratio of movement of that disk to its maximum intrusion into the space between the magnet and armature determine approximately the relative drag experienced at the different positions within the range of its intruding movement. But from the above description, one familiar with the subject will be able to adapt the levers in respect to their proportions and positions to the material chosen for the case and lever supports, and the width of the cylindrical member of the drag dish or of its intruding portion.

It will be obvious that the lever system 3.25 could be greatly modified without departing from the principle of the invention, and that the number of levers in the system\ is not limited to the two levers shown, constitilting the so-called lever couple.

liti- .the entire lever system, including the support and both levers, ready for insertion in the case but this is obviously a matter of indifference so far as the operation of the device is concerned, and I do not limit myself to this or any particular way' of supporting and affording stops for the levers.

It will be seen, also, upon consideration, that the adjustment of the stop 28, which, as above described, will be made so as to position the parts for giving the biased element of the drag disk the necessary intrusion be- .tween the magnet and armature for proper speed indication at the temperature to which the parts are assembled, amounts to calibrating the instrument, and it will be evident, therefore, that this adjustable stoplmay'be employed for rev-calibrating or readjusting the instrument tocompensate for permanent changes which may occur, such as change in the strength of the I claim 1. In a magnetic speedometer, in combination with a case, a magnet andnon-magnetic ele1nent,'bearings in which said, magnet and non-magnetic element are mounted in the permanent magnet.

ease for rotation; means for biasing one of said parts to a predetermined position of rest, and a spindle upon which said biased part is mounted for rotation; a lever support of material having a different cdetlicient of expansion from the material of ,the case, mounted thereon and extending from side to side thereof; an initial lever fulcrumed and stopped near one end of the lever support and the case wall, the fulcrum being on one of said last-mentioned two parts and the stop on the other; a final lever fulcrumedand engaged at the other end of the lever support and the preceding lever, remote from the fulcrum of the latter, the fulcrum being on one of said last-mentioned two parts and the engagement with the other; and a step-bearing for the spindle of the biased element lodged upon said final lever at a point remote, from the fulcrum and engagement of the latter. 2. In a magnetic speedometer, in combination with a case,. a magnet and non-magnetic element, hearings in which said magnet and nonmagnetic-element are mounted in the case for rotation; means for biasing one of said parts to a predetermined position of rest, and a spindle upon which said biased part is mounted for rotation; a stepbearing for said spindle; a lever system comprising a lever support mounted on the case' and stopped against one side "thereof and extending across the case; an in'itlal lever of said system having a bearing on the side of the case remote from that at which the lever support is stopped; and a final lever of the system positioned for supporting the Step bearing.

netic element, bearings in which said mag net and non-magnetic element are mounted in the case for rotation; means for biasing one of said parts to a predetermined position of rest, and a spindle upon which said biased part is mounted for rotation; a step-bearing for said spindle; a lever support of material having different coefficient of expansion from the material of the case, mounted on the case, stopped thereagainst atone side; and extending acrossthe case; a lever which supports the step-bearing, having its fulcrum substantially fixedwith respect to thecase at the end of the lever support which is stopped on the case; a lever engaged with the case and with the lever support at the opposite end of the latter, and extending to the first-mentioned lever and engaged therewith near the fulcrum of the latter.

4. In a magnetic speedometer, in combination with a case, a magnet and nondnagnetic element,'bearings in which said magnet and non-magnetic element are mounted in the case for rotation; means for biasing one of said parts to a predetermined posi tion of rest, and a spindle upon which said biased-part is mounted for rotation; a stepbearing for the spindle; a lever support-of material having different coefiicient of expansion from the case, mounted on the. case and stopped against one side thereof; a lever which supports the step bearing, having its fulcrum fixed with respect to the case at the side thereof at which the'lever support is stopped; and a lever fulcrumed on the lever supportiaothe opposite end thereof, and having a short arm stopped against the case near its fulcrum anda long arm extending to the first-mentioned lever and engaged therewith near the fulcrum of the latter.

5. In at magnetic speedometer, in combin'ation with a case, a magnet and non-magnetic element, bearings in which said magnet and a non-magnetic element are mountedv in the case for rotation; means for biasing one of said parts to a predetermined position of rest, and a spindle upon which said biased part is mounted for rotation; a step-bearing for the spindle: a lever support and means by which it is fixed on the case in position to be stopped thereagainst at one side thereof; a lever which supports the-step-bearing fulcrumed on the lever support at its stopped end, and a lever fulcrumed on the lever support at the opposite end of the latter, having a short arm stopped against the case and a long arm extending to the first-mentioned lever and engaged therewith 1 near the fulcrum ot' the latter.

6. In an instrument of the character indihissed element, a step-bearing for the same; lever means supported on the case on which the s) p-bearing is supported; and n screw set nough the ease and operating against the lever mechanism for edit ring the positioi he step bearing.

'Z, in a magnetic speedometer, in comhinetion with a case; a magnet and a non- :nragnetie element; a post on which the magnet is mounted for rotation and means by which it"is supported rigidly within the case with both ends spaced away from the opposed walls of the case; said post being axially npertiiired from end to end", a spindle on. which the non-magnetic element is mounted, extending within said axial aperture of the post; a bearing on which one end of the spindle is stopped and means by which it is supported on the case; a dial plate mounted on the case through which the other end ol? the spindle protrudes, and an index hand on the protruding end of the spindle 8. in a. magnetic speedometer, in combination with a case; a magnet of substantially ring form and n nonmagnetic element of cup form havingdts cylindrical wall or flange encompaessing the ring-shaped magnet; a, post upon which the magnet is mount ed for rotation about its axis, and means by which it is supported in the case said post having both of itsmrnds spaded-away "from the case,-and being axially apertured from end to end; a spindle upon which the nonmagnetic element is mounted, said spindle being extended within said axially hollow post; a step bearing in which one end of the spindle is stepped, and means by which said eiepbearing is supported on the case, a hearing member tor the other end of the spindle supported on the case, a biasing spring connected at one end to said bearing member and at the other end to the spindle.

9. in a magnetic speedometer, in combinationwith a case; an annular magnet and non-magnetic element in cup term having its cylindrical wall encompassing the magnot; a pest and means by which it is mounted rigidly within. the case having both its ends spaced away from the case; said post beinn; axially apertured from end to end; a spindle uponwhich the non-magnetic element is mounted, extending within said holi ,ovome low post; a bearing in which one end of the spindle is stepped, and means by which sa1d bearing is supported on the case, a dial plate mounted on the case and through which the other end of the spindle extends; an index linger carried by said end of the protruding spindle.

10. In a magnetic speedometer, in combination with a case; a magnet and a nonmngnet' elen'ient; a post upon which the magnet. is mounted for rotation, and means by which it is supported fixedly in the ease with both its ends spaced away from the case well; said post being axially apertured from end to end; a spindle upon-which the non-magnetic element is mounted extending within the axial aperture of the poet; a bearing supported on the case on which one end of the spindle is stopped, and means for supporting said bearing extended past the end of the post and between the same and the opposed wall of the case; a bearing member supported on the case and extend ing past the opposite end of the post; a spindle having a bearing in seid member and a biasing spring having one end connected to the member and the other end to the spindle.

ll. ln a magnetic symedometer, in combination with a case; a magnet and a non magnetic element in the vase; post upon which the magnet is mounted for rotation, and means by which the post is mounted rigidly within. the case said. post having both its ends spaced away from the wall of the case, and being axially apertured from end to end; a spindle upon which the non-magnetic element is mounted, extending within the axial apertureof the post; a bearing supported on the case and on which one end of the spindle is stepped; a support for said bearing extended past one end of the post between the same andthe proximate wall of theease; and means for. moving said sup port toward and from the end of the post.

ln testimony whereof, I hevehereunto set. my hand, at Chicago, Illinois, this 25th day of July, 1910.

.J'onin K. STEWART.

lVitnesses: CHAS. S. BURToN, Jenn ELLIO'IT. 

